WASHINGTON (CNN) -- Republican presidential candidate Mike Huckabee said it was "heartbreaking" that the deaths of women killed by a convicted rapist who was released from prison after Huckabee supported his parole had become politicized.

On Wednesday, the mother of the woman the convict later murdered pledged to campaign against the former Arkansas governor.

"There are families who are truly, understandably and reasonably, grief stricken," Huckabee told CNN. "And for people to now politicize these deaths and to try to make a political case out of it rather than to simply understand that a system failed and that we ought to extend our grief and heartfelt sorrow to these families, I just regret politics is reduced to that."

The case of the rapist, Wayne DuMond, began in 1985, when he was accused of raping a 17-year-old girl. He was later convicted and sentenced to a life term.

Before trial, DuMond was attacked in his home and castrated, and the local sheriff kept the severed testicles in a jar. No charges were brought in the attack.

Less than a year after his release from prison in 1999, DuMond was accused of raping and murdering Carol Shields, a woman in Kansas City, Missouri. DuMond was convicted of the crime in 2003. He died in prison in 2005.

Huckabee on Sunday confirmed to CNN he had sent the letter to DuMond.

The murdered woman's mother, Lois Davidson, said she will "absolutely campaign against" Huckabee, and said she decided to come forward when he started doing well in the polls.

"It's because he is a serious contender," Davidson said. "I didn't think he had a chance, but now he's right up there in Iowa."

Huckabee said he had considered granting DuMond clemency in 1996, but he dropped the idea in response to public outcry and because he wanted to ensure DuMond was supervised when he was released from prison.

"Had I granted his commutation, then there would have been no supervision at all," Huckabee said, "I wasn't comfortable with that."

Don't Miss

When he spoke about the case, Huckabee suggested his role in the decision to parole DuMond was limited.

Huckabee said it was the decision by former Arkansas Govs. Bill Clinton and Jim Guy Tucker that made DuMond eligible for parole, and Huckabee declined to reduce DuMond's sentence further.

"I've never made a decision about the DuMond case other than the decision to write the letter" to DuMond, Huckabee said. "That was my decision, but I didn't parole him, because governors don't parole people in Arkansas."

However, Charles Chastain, a parole board member at the time, told ABC News he felt pressure from Huckabee when the board considered DuMond's parole in 1996, and the Arkansas Times reported in 2002 that two other board members said they were influenced by Huckabee to parole DuMond.

Huckabee denied he asked the board to approve DuMond's parole.

"No, I did not," Huckabee said Sunday. "Let me categorically say I did not."

Huckabee noted that the three board members who said they were pressured were appointed to the board by Democrats Clinton and Tucker.

Huckabee said Wednesday his discussion with the parole board in 1996 was a general discussion about clemency, not about the DuMond case.

But a former Huckabee aide, Butch Reeves, tells CNN that the DuMond case was discussed during the meeting with the parole board, but that it was the board members who asked Huckabee about the case. Reeves said Huckabee did not pressure the board to approve DuMond's parole.

Documents posted on the Web site The Huffington Post indicate Huckabee received letters from several victims of DuMond before his release.

The letters detailed his past actions and pleaded that he remain incarcerated.

"I feel that if he is released it is only a matter of time before he commits another crime and fear that he will not leave a witness to testify against him the next time," one victim wrote. She described how DuMond had raped her at knifepoint.

A former top Huckabee aide confirmed to CNN that the then-governor received that letter and a follow-up phone call from the victim.E-mail to a friend